BIST™ (Beads array In Single Tip) technology has been developed as a technique for simultaneously detecting a plurality of target substances for analysis (Non-Patent Document No. 1). BIST™ is a device comprising probe beads 1 mm in diameter aligned and sealed in a cylindrical tip (hereinafter, referred to as “capillary”). These beads individually carry an immobilized biological molecule (e.g., antibody, antigen or DNA fragment) that binds to a target substance for measurement such as antigen or gene. Since this BIST™ can fit to the nozzle of a Magtration™ apparatus, it is possible to carry out hybridization or antigen-antibody reaction and washing operation using the same automated apparatus that is used for nucleic acid extraction (e.g., Magtration™ System 6GC or Magtration™ System 12GC plus, both manufactured by Precision System Science). The signal generated therefrom is detected with a scanner (e.g., BIST™nner manufactured by Precision System Science).
The biggest technical feature of BIST™ is that a plurality of probe beads for capturing different target substances are aligned in a capillary, thus enabling simultaneous detection of multi-items. In the application of BIST™ to quantitative examination of thyroid stimulating hormone (TSH), as well as FT3 (Free Triiodo thyronine) and FT4 (Free Thyroxine) which are clinically highly useful when examined simultaneously with TSH, the range of detection concentrations required in practice extends broadly (TSH: 0.05-50 μIU/mL, FT3: 0.5-20 pg/mL, FT4: 0.1-10 ng/dL; approximately 103 in dynamic range). For this reason, in order to perform multi-item simultaneous examination, the signal light from each probe bead (light whose intensity increases in proportion to the concentration of the target substance) should be localized to thereby suppress the interference with the signal light from other probe beads. However, no satisfactory localization of signal light has yet been achieved to date.